1. Field of the Invention
This invention relates to a process and an apparatus for drying solvent containing material.
2. Description of the Prior Art
A process and an apparatus for drying solvent containing material are known from U.S. Pat. No. 4,150,494, in which a conveyor supporting the solvent containing material to be dried by evaporation, is conducted through a drying chamber containing inert gas (nitrogen), the drying chamber is bounded on both sides by lock chambers. The inert gas is introduced through the lock chambers. The major part of the inert gas stream flows into the drying chamber and is laden with solvent vapors therein. After leaving the drying chamber, solvent vapors are removed from the inert gas by cooling in a heat exchanger and the inert gas is discharged to the atmosphere. The minor part of the inert gas flows out of the lock chamber directly into the atmosphere and has the function of preventing air which contains oxygen from entering the drying chamber.
It was found that in such a process entry of atmospheric oxygen into the drying chamber and exit of inert gas laden with solvent vapors into the atmosphere cannot be completely prevented. Entry of atmospheric oxygen is particularly undesirable when the inert gas stream containing the solvent vapors is to be returned to the drying chamber, since there occurs a constant enrichment of atmospheric oxygen so that when inflammable solvents are used, the explosion limits can be reached or exceeded. In addition, exit of solvent vapors into the atmosphere is undesirable because of the economic losses entailed and because of environmental pollution.
An object of the present invention is to provide a process and an apparatus for drying solvent containing material and enabling exit of solvent vapors from and preventing entry of air into, a drying chamber containing inert gas and through which a solvent containing material is passed.
This object and others is achieved in accordance with the invention.